Isolation of delta isomer of benzene hexachloride



United States atet ISOLATIGN F DELTA ISOMER 0F BENZENE HEXACHLORIDE Arnold. N. Johnson, Paterson,: N. J., assignor to Commercial Solvents Corporation, Terre Haute, Ind, a eerporation of Maryland No Drawing. Application March 23, 1953, SerialNo. 344,189

5 Claims. (Cl. 260-648) My invention relates to benzene hexachloride and more particularly to a process for the isolation of the delta isomer of benzene hexachloride from amixture of all the isomers of benzene hexachloride.

Benzene hexachloride, also known as 1,2,3,4,5,6-hexa'- chlorocyclohexane, is generally prepared by the additive chlorination of benzene in the presence of actinic radiation. Benzene hexachloride as prepared in this manner, is made up of a mixture of at least five benzene hexachloride isomers together with smallarnounts" of heptachlorocyclohexane and octachlorocyclohexane. The com ponents of the mixture are generally present in amounts as follows: gamma isomer 12 to 14%, beta isomer 3 to 7%, delta isomer 5 to epsilon isomer 2-to 5%, alpha isomer 55 to 70%, heptachlorocyclohexane 2 to 5%, and octac'hlorocyclohexane 0.2 to 1%.

Benzene hexachloride is a well known insecticide, however, the gammaisomer of benzene hexachloride is the only. one of the isomers which possesses this insecticidal activity and the remaining isomers have heretofore been thoughtto be of little value. Recently it has been found that the delta isomer has irritant properties of its-own as well as considerable toxic activity against snails. Furthermore, the delta isomer has been found to be an effective anthelminitic agent for animals.

I have now discovered a process for separating the delta isomer from the remaining isomers of benzene hexachlo ride and thereby obtain, in substantially pure form, the delta isomer of benzene ihexachloride which hasnow been found to be of considerable value in various applications.

My new process consists essentially of first preparing an-85- to 90%"delta isomermaterial by extracting other isomers and impurities from a delta oil containing at least about 40% of the delta isomer and not more than about /3 of the delta isomer content as the alpha isomer, the 85 to 90% delta isomer material remaining as an insoluble cake. I then purify the 85 to 90% delta isomer material by heating it with a solvent in which the delta isomer is much more soluble than any of the other isomers to obtain a saturated solution of delta isomer and then cooling to crystallize the substantially pure delta isomer as a white crystalline material having a melting point of 136-138" C.

The delta oil starting material which I employ in my process containing at least about 40% of the delta isomer and not more than about /3 the delta isomer content as alpha isomer can be prepared by any suitable means but a convenient method and one Which I prefer to employ is that disclosed by Leslie J. Burrage in United States Patent 2,603,664, patented July 15, 1952. The delta oil obtained according to the method of this patent contains all of the benzene hexachloride isomers except that a large proportion of the alpha and beta isomers has been removed.

In carrying out my invention, I first extract the delta oil (the mixture of isomers of benzene hexachlonide containing at least about 40% of the delta isomer) with a solvent in which the gamma isomer is at least about 40% 2,803,673 Patented Aug. 20, 1957 2 more soluble than the delta isomer. Suitable solvents for this step in my invention include chlorinated hydrocarbons such. as,,for example, chloroform, carbon tetrachloride, perchlorethylene, 1,1,2-trichloroethane, trichloroethylene, etc. This extraction procedure removes benzene hexachloride isomers other than the delta isomer aswell as impurities from the delta oil and leaves behind as an insoluble cake, a material containing about to delta isomer of. benzene hexachloride. This material is the so-calledjtechnical delta.

The technical delta i. e., material containing about85 to 90% delta isomer of benzene hexachloride, isthen treated toipurify the delta isomer by heating it with'a solvent, hereinafter more particularly described, to form a saturated solution of the delta isomer, filtering the solution at the elevated temperature, and allowing the filtrate to cool to crystallize the substantially puredelta isomer of benzenehexachloride. The temperature to which I heat the mixtureof technical delta and solvent is limited; of course, b'ythe boiling point of the solvent but if possible should be about 40 to 50 C. After heating, the insoluble impurities are removedbyany suitable means, such as for example, byfiltration and the filtrate cooled to room temperature to precipitate the substantially pure delta isomer of benzene hexachloride. The solvent which I employ for this particular step in my process canbe any solvent in Whichthe delta isomer is at least about 40% more soluble than the gamma isomer and one which has a high enough boiling point so that vaporization of the solvent upon heating the mixtureof technical delta and solvent does not adversely affect the results. I havefound that suitable solvents include hydrocarbons, such as, for example, benzene, toluene, xylene, naphtha (B. P. 230- 270 C.), etc.; alcohols, such as, for example, lower aliphatic alcohols containing up to about five carbon atoms, glycerol, diacetone alcohol, cyclohexanol, tetrahydrofur- 'furyl' alcohol, 2-ethoxy-l-ethanol, etc; aliphatic esters, such as, for example, methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, pentacetate, methyl propionate, ethyl carbonate, Z-ethoxyethyl acetate, etc. Ethers generally have a. boiling point which is too low for use. in my process although some ethers such as, for example, isopropyl ether, butyl ether, 1,4-dioxane, etc. can beemployed. Ketones, such as,.for example, acetone, can be employed although I prefer to employ other of the abovementioned solvent materials rather than a ketone.

The following examples are offered to illustrate my invention and I do not intend to be limited to the specific materials, proportions, or procedures outlined therein. I intend for all equivalents obvious to those skilled in the art to be included Within the scope of my invention as described in this specification and the attached claims.

Example I A two-hundred pound portion of technical benzene hexachloride obtained by the additive chlorination of benzene in the presence of actinic radiation Was mixed with 320 pounds of methanol, and the insoluble alpha isomer amounting to 147 pounds was removed from the mixture, leaving 321 pounds of a 16% by weight solution of benzene hexachloride in methanol. The methanol solution of benzene hexachloride was then concentrated to give a solution of 30% benzene hexachlo-ride in methanol after Which 39 pounds of Water was added to make a solution of 75% methanol and 25% water. The result ing precipitate which formed was removed by filtration and dried to obtain 31.6 pounds of a material containing 57.7% gamma isomer of benzene hexachloride. The aqueous methanol filtrate was found to contain 12.6 pounds of solid of which 48.8% was the delta isomer, 4.9% alpha isomer, and 9.0% gamma isomer.

Example 11 The material containing 48.8% delta isomer obtained in Example I was then extracted with carbon tetrachloride using 159 grams of carbon tetrachloride per 100 gram 'portion of the material containing 48.8% delta isomer of benzene hexachloride. The insoluble cake which remained after filtration of the carbon tetrachloride insoluble material amounted to 29 grams of which 86.5% was the delta isomer of benzene hexachloride. This was the so-called technical delta.

Example III A' benzene hexachloride material containing 47.2% delta isomer, 11.7% alpha isomer and 13.1% gamma isomer was extracted with an equal amount of perchloroethylene; The insoluble cake remaining after filtration was a technical delta material containing 89.3% delta isomer of benzene hexachloride.

Example IV 100 gram portion of technical delta material containing 86.5% delta isomer of benzene hexachloride, obtained as in Example II, was mixed with 100 grams of benzene and the material heated to 50 C. The mixture was filtered while hot and the filtrate of 175 grams then cooled to 22 C. to crystallize the substantially pure delta isomer of benzene hexachloride as a white crystalline material having a melting point of 136.5138 C.

Example V A 100 gram portion of technical delta material containing 89.3% delta isomer of benzene hexachloride obtained as in Example III was mixed with 150 grams of ethyl alcohol and the material heated to 45 C. The mixture was filtered while hot and the filtrate then cooled to 20 C. to crystallize the substantially pure delta isomer of benzene hexachloride as a white crystalline material having a melting point of 136-138 C. Now having described my invention, What I claim is: 1. A process for the purification of the delta isomer of benzene hexachloride which comprises extracting a mixture of all benzene hexachloride isomers containing at least about 40% delta isomer and not more than about /3 the delta isomer content as alpha isomer with carbon tetrachloride, removing the insoluble residue, extracting the said delta isomer-containing residue with an amount of benzene, such that the resulting solution is substantially saturated with the delta isomer, removing benzene insoluble materials at a temperature of at least about 40 C. and then cooling the resulting solution to crystallize the substantially, pure delta isomer of benzene hexachloride. 2. A process for the purification of the delta isomer of benzene hexachloride which comprises extracting a mixture of all benzene hexachloride isomers containing at least about 40% delta isomer and not more than about /3 the delta isomer content as alpha isomer with perchloroethylene, removing the insoluble residue, extracting the said delta isomer-containing residue with an amount of benzene, such that the resulting solution is substantially saturated with the delta isomer, removing benzene insoluble materials at a temperature of at least about 40 C. and then cooling the resulting solution to crystallize the substantially pure delta isomer of benzene hexachloride.

3. A process for the purification of the delta isomer of benzene hexachloride which comprises extracting a mixture of all benzene hexachloride isomers containing at least about 40% delta isomer and not more than about /3 the delta isomer content as alpha isomer with carbon tetrachloride, removing the insoluble residue, extracting the said delta isomer-containing residue at an elevated temperature with an amount of a lower aliphatic alcohol such that the resulting solution is substantially saturated with the delta isomer, removing the insoluble materials from the solution at the said elevated temperature and then cooling the resulting solution to crystallize the substantially pure delta isomer of benzene hexachloride.

4. The process of claim 3 wherein the lower aliphatic alcohol is ethyl alcohol. I g

5. A process for the purification of the delta isomer of benzene hexachloride which comprises extracting a mixture of all benzene hexachloride isomers containing at least about 40% delta isomer and not more than about /3 the delta isomer content as alpha isomer with a solvent selected from the group consisting of carbon tetrachloride, perchloroethylene, and chloroform, removing the insoluble residue, extracting the said delta isomer-containing residue at an elevated temperature with an amount of a solvent selected from the group consisting of a lower aliphatic alcohol, benzene, toluene, xylene, and naphtha, such that the resulting solution is substantially saturated with the delta isomer, removing the insoluble materials from the solution at the said elevated temperature and then cooling the resulting solution to crystallize the substantially pure delta isomer of benezene hexachloride.

OTHER REFERENCES Van der Linden, Ber. der deut. Chem. GeselL, vol. 45, pp. 231-6 (1912). 

5. A PROCESS FOR THE PURIFICATION OF THE DELTA ISOMER OF BENZENE HEXACHLORIDE WHICH COMPRISES EXTRACTING A MIXTURE OF ALL BENZENE HEXACHLORIDE ISOMERS CONTAININGG AT LEAST ABOUT 40% DELTA ISOMER AND NOT MORE THAN ABOUT 1/3 THE DELTA ISOMER CONTENT AS ALPHA ISOMER WITH A SOLVENTT SELECTED FROM THE GROUP CONSISTING OF CARBON TETRACHLORIDE, PERCHLOROETHYLENE, AND CHLOROFORM, REMOVING THE ISOLUBLE RESIDUE, EXTRACTING THE SAID DELTA ISOMER-CONTAINING RESIDUE AT AN ELEVATED TEMPERATURE WITH AN AMOUNT OF A SOLVENT SELECTED FROM THE GROUP CONSISTING OF A LOWER ALIPHATIC ALCOHOL, BENZENE, TOLUENE, XYLENE, AND NAPHTHA, SUCH THAT THE RESULTING SOLUTION IS SUBSTANTIALLY SATURATED WITH THE DELTA ISOMER, REMOVING THE INSOLUBLE MATERIALS FROM THE SOLUTION AT THE SAID ELEVATED TEMPERATURE AND THEN COOLING THE RESULTING SOLUTION TO CRYSTALLIZE THE SUBSTANTIALLY PURE DELTA ISOMER OF BENEZENE HEXACHLORIDE. 